Cephalexin¶
Overview¶
| Field | Detail |
|---|---|
| Drug class | 1st generation cephalosporin |
| Route | Oral |
| Forms | 250 mg, 500 mg tablets; 125 mg/5 mL, 250 mg/5 mL suspension |
| Storage | Room temp before; refrigerate suspension after mixing |
Preparation for Oral Challenge¶
Before you start
Ensure the patient has fasted if required. Use a calibrated oral syringe for all volumes. Check the concentration of the suspension (125 mg/5 mL or 250 mg/5 mL).
Reagents¶
- Cephalexin Suspension (e.g., Keflex)
- Syringes: 1 mL, 3 mL, 5 mL, 10 mL oral syringes
Step-by-step Challenge Protocol¶
Using 125 mg/5 mL (25 mg/mL) Suspension:¶
| Step | Dose | Volume | Cumulative Dose |
|---|---|---|---|
| 1 | 25 mg | 1.0 mL | 25 mg |
| 2 | 50 mg | 2.0 mL | 75 mg |
| 3 | 100 mg | 4.0 mL | 175 mg |
| 4 | 250 mg | 10.0 mL | 425 mg |
Challenge Protocol¶
Intervals: Observe for 30–60 minutes between each step. Final Observation: Monitor for 1–2 hours after the final dose.
Notes¶
- Cephalexin is the most common oral 1st generation cephalosporin.
- Cross-reactivity with Amoxicillin and Ampicillin is common due to shared side chains.
- Not routinely used for skin testing. If required, test with Cefazolin and Penicillins.